UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D. C. 20549

FORM 10-Q/A

(Amendment No. 1)

for the quarterly period ended December 29, 2012.

For the transition period from                      to                     

Commission File Number 001-32833

TransDigm Group Incorporated

(Exact name of registrant as specified in its charter)

Delaware

(State or other jurisdiction of incorporation or organization)

41-2101738

(I.R.S. Employer Identification No.)

(216) 706-2960

(Registrant’s telephone number, including area code)

(Former name, former address and former fiscal year, if changed since last report.)

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    YES  x    NO  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate website, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    YES  x    NO  ¨

Indicate by check mark whether the registrant is a large accelerated filer, accelerated filer, non-accelerated filer, or smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    YES  ¨    NO  x

The number of shares outstanding of TransDigm Group Incorporated’s common stock, par value $.01 per share, was 50,040,455 as of January 26, 2013.

Explanatory Note

TransDigm Group Inc. (“TD Group”) is filing this Amendment No. 1 (the “Form 10-Q/A”) to our Quarterly Report on Form 10-Q for the quarter ended December 29, 2012, which was filed with the Securities and Exchange Commission on February 5, 2013 (the “Original Filing”). We are filing this amendment to correct our certifications under Section 302 of the Sarbanes-Oxley Act of 2002, which inadvertently omitted certain required provisions regarding internal controls over financial reporting. The corrected certifications are included as Exhibits 31.1 and 31.2 to this Form 10-Q/A.

Except as specifically noted above, this Form 10-Q/A does not modify or update disclosures in the Original Filing. Accordingly, this Form 10-Q/A does not reflect events occurring after the filing of the Original Filing or modify or update any related or other disclosures.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

TRANSDIGM GROUP INCORPORATED

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EXHIBIT INDEX

TO FORM 10-Q/A FOR THE PERIOD ENDED DECEMBER 29, 2012

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